The present invention relates generally to fluid drop ejectors, and more particularly to a restriction within fluid cavity of fluid drop ejector.
Fluid drop ejectors have been developed for ejecting droplets of a flowable material in a controlled manner. As illustrated in FIGS. 1A and 1B, a conventional fluid drop ejector 90 includes a cylindrical body 92, a circular flexible membrane 94 having an orifice 96 defined therein, and an annular actuator 98. The cylindrical body defines a reservoir for holding a supply of flowable material and the circular flexible membrane has a circumferential edge clamped to the cylindrical body. The annular actuator includes a piezoelectric material which deforms when an electrical voltage is applied. As such, when the piezoelectric material deforms, the circular flexible membrane deflects causing a quantity of flowable material to be ejected from the reservoir through the orifice.
One application of a fluid drop ejector is in an inkjet printing system. As such, the inkjet printing system includes a printhead having a plurality of fluid drop ejectors that eject droplets of ink through orifices or nozzles to form an image on a print medium. By increasing a velocity of droplets ejected from the fluid drop ejectors, trajectory errors of the droplets are minimized. As such, image quality of the inkjet printing system is enhanced.
One way to increase a velocity of droplets from the fluid drop ejector is to increase a pressure of fluid throughout the reservoir or fluid cavity of the fluid drop ejector. However, increasing a pressure of fluid throughout the fluid cavity requires that a stiffness of the flexible membrane be increased since the flexible membrane must sustain the pressure generated throughout the fluid cavity. Unfortunately, increasing the stiffness of the flexible membrane reduces a compliancy or flexibility of the flexible membrane and requires that a greater force be applied to deflect the flexible membrane.
Accordingly, a need exists for a fluid drop ejector which provides an increased velocity of droplets which are ejected from the fluid drop ejector. More particularly, a need exists for a fluid drop ejector which increases a pressure on fluid within a fluid cavity of the fluid drop ejector without requiring an increased stiffness of a flexible membrane of the fluid drop ejector.
One aspect of the present invention provides a fluid drop ejector. The fluid drop ejector includes a substrate having a fluid cavity defined therein, a flexible membrane supported by the substrate and having an orifice defined therein which communicates with the fluid cavity, an actuator associated with the flexible membrane and adapted to deflect the flexible membrane relative to the substrate in response to an electrical signal, and a restriction positioned within the fluid cavity opposite the orifice As such, the restriction defines a confining region of the fluid cavity adjacent the orifice and a perimeter of the restriction is spaced from a sidewall of the fluid cavity.
Another aspect of the present invention provides a method of forming a fluid drop ejector. The method includes defining a fluid cavity in a substrate, supporting a flexible membrane by the substrate, communicating an orifice of the flexible membrane with the fluid cavity, positioning a restriction within the fluid cavity opposite the orifice, and associating an actuator with the flexible membrane, wherein the actuator is adapted to deflect the flexible membrane relative to the substrate in response to an electrical signal.
Another aspect of the present invention provides a method of ejecting droplets of a fluid. The method includes supplying a fluid cavity with the fluid, supporting a flexible membrane having an orifice defined therein over the fluid cavity so as to communicate the orifice with the fluid cavity, confining the fluid within the fluid cavity in a region adjacent the orifice with a restriction having a perimeter spaced from a sidewall of the fluid cavity, and deflecting the flexible membrane relative to the fluid cavity and ejecting a droplet of the fluid through the orifice of the flexible membrane.
Another aspect of the present invention provides an inkjet printing system. The inkjet printing system includes a substrate having a plurality of fluid cavities formed therein, a plurality of flexible membranes each supported by the substrate and having an orifice defined therein which communicates with one of the fluid cavities, a plurality of restrictions each positioned within one of the fluid cavities opposite the orifice of a respective one of the flexible membranes, and a plurality of actuators each associated with one of the flexible membranes. As such, each of the restrictions define a confining region of the one of the fluid cavities adjacent the orifice of the respective one of the flexible membranes and a perimeter of each of the restrictions is spaced from a sidewall of a respective one of the fluid cavities. In addition, each of the flexible membranes is adapted to deflect in response to application of an electrical signal to an associated one of the actuators.